This investigation will examine the effectiveness of a cognitive-behavioral relapse prevention program in contrast with a general discussion group approach in treating adult chronic marijuana smokers. The relapse prevention program, an intervention intended to enhance the maintenance of control, focuses on beliefs about quitting, skills in coping with difficulties while abstaining, and achieving balance in lifestyle. Objective criteria for the assessment of marijuana abuse (and the screening out of those currently abusing alcohol and/or other drugs) will be employed in selecting 208 subjects who will subsequently be randomly assigned to the two treatment conditions. The interventions are designed to take place in 8 to 12-person groups co-led by two therapists. Each group will meet for ten two-hour sessions over an eleven week period. Follow-up assessments will be conducted at 1, 3, 6, 9, and 12 months following termination. Specific measures designed to test the theoretical framework of the relapse prevention model will be incorporated in the baseline, in-treatment, and follow-up assessment instruments. Subject self-report, corroborative reports from an individual in the subject's social network, and urinalysis data will be utilized in this research.